The invention relates to a process for the production of 4-amino-2-chloro-5-cyano-6-(methylthio)pyrimidine (I) of the formula: ##STR1## wherein 2-chloropyrimidines are intermediate products for the synthesis of 2-aminopyrimidines, a class of substances which contains numerous effective pesticides. 2. Background Art
An important representative of the 2-chloropyrimidines is 4-amino-2-chloro-5-cyano-6-(methylthio)pyrimidine, whose methylthio group can be nucleophilically exchanged optionally after oxidation to the methanesulfonyl group [European Published Patent Application No. 0244360].
The known process for the production of 4-amino-2-chloro-5-cyano-6-(methylthio)pyrimidine [H. Kristinsson, J. Chem. Soc. Chem. Commun., (1974), page 350] starts from cyanamide and carbon disulfide, which with potassium hydroxide yield the dipotassium salt of cyanimidodithiocarbonic acid [A. Hantzsch and M. Wolvekamp, Justus Liebigs Ann. Chem., Vol. 331, (1904), page 282]. This is reacted with dimethyl sulfate to dimethyl cyanimidedithiocarbonate which adds malononitrile in the presence of sodium methylate. By adding hydrochloric acid the addition product is cyclized to the corresponding pyrimidine. In this way, not only the desired product results but also the isomeric 2-amino-4-chloro-5-cyano-6-(methylthio)pyrimidine, namely in the ratio of 3:2 (2-amino/4-amino-) so that with a total yield of 88 percent, the effective yield is only about 35 percent.